Changes in the mucosal expression of interleukin 15 in Helicobacter pylori-associated gastritis

Transcripts for interleukin (IL) 15 were detected in the gastric mucosal samples of 5/5 (100%) patients with no evidence of Helicobacter pylori infection and in 4/14 (28%) H. pylori-infected patients (P<0.05). Both IL-15 mRNA and IL-15 protein were detected in 1/6 (17%) patients who successfully underwent H. pylori eradication therapy, before treatment and in 5/6 (83%) cases after eradication. Even though a parallel significant (P<0.03) improvement of gastritis score occurred after eradication, the severity of gastritis did not differ according to the mucosal IL-15 expression among H. pylori-infected patients, irrespective of the CagA serology. This study demonstrates, for the first time, that transcripts for IL-15 are expressed in the human gastric mucosa. Changes occurring during H. pylori colonisation and after eradication raise the hypothesis that H. pylori may down-regulate IL-15 expression in the gastric mucosa.